As one of ionization methods in mass spectrometry, Matrix Assisted Laser Desorption/Ionization (MALDI) is known. In the MALDI process, to analyze an analyzing object that is less likely to absorb laser light or an analyzing object that is susceptible to damage by laser light, such as protein, an analyzing object is dispersed in a material that absorbs laser light easily and is ionized easily (matrix) to form a sample, and then the sample (the matrix and the analyzing object) is irradiated with laser light to be ionized.
In a mass spectrometer using the MALDI process, in general, a sample is arranged on a plate made of metal, which is called a sample plate (or a target plate), and the sample arranged on the plate is irradiated with laser light. At this time, a voltage is applied to the plate as needed to accelerate ions generated with irradiation of laser light.
As a conventional art described in a gazette, use of a sample plate in the MALDI process is described, in which the sample plate includes an electrically conductive rectangular stainless steel substrate having a first surface, and the first surface is coated with a hydrophobic coating of a synthetic wax, natural wax, lipid, organic acid, ester, silicon oil, or silica polymers (refer to Patent Document 1).
In addition, as another conventional art described in a gazette, use of a sample plate in the MALDI process is described, in which the sample plate includes an electrically conductive stainless steel substrate having a first surface, and at least a portion of the first surface is coated with a composite coating that includes a hydrophobic coating and a coating of a thin film mixture of a matrix and an intercalating polymer (refer to Patent Document 2).